SmackDebugger initialization moved to dedicated factory.

You can set your custom debugger class as before, by using clear api
method ReflectionDebuggerFactory.setDebuggerClass, or you can set custom
debugger factory using SmackConfiguration.setDebuggerFactory if it's not
enough flexible for your needs

smack-debug-slf4j/src/main/java/org/jivesoftware/smackx/debugger/slf4j/SLF4JDebuggerFactory.java

@@ -0,0 +1,35 @@
+/**
+ *
+ * Copyright 2014 Vyacheslav Blinov
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jivesoftware.smackx.debugger.slf4j;
+
+import org.jivesoftware.smack.XMPPConnection;
+import org.jivesoftware.smack.debugger.SmackDebugger;
+import org.jivesoftware.smack.debugger.SmackDebuggerFactory;
+
+import java.io.Reader;
+import java.io.Writer;
+
+/**
+ * Implementation of SmackDebuggerFactory which always creates instance of SLF4JSmackDebugger
+ */
+public class SLF4JDebuggerFactory implements SmackDebuggerFactory {
+    @Override
+    public SmackDebugger create(XMPPConnection connection, Writer writer, Reader reader) throws IllegalArgumentException {
+        return new SLF4JSmackDebugger(connection, writer, reader);
+    }
+}

smack-debug-slf4j/src/main/java/org/jivesoftware/smackx/debugger/slf4j/SLF4JSmackDebugger.java

@@ -58,7 +58,7 @@ public class SLF4JSmackDebugger implements SmackDebugger  {
      * Makes Smack use this Debugger
      */
     public static void enable() {
-        SmackConfiguration.setDebugger(SLF4JSmackDebugger.class);
+        SmackConfiguration.setDebuggerFactory(new SLF4JDebuggerFactory());
     }
 
     /**